PubMed · 175151
The source did not provide an abstract. Follow the original record for more information.
Explore connections, maps & timelines
B Matthews. 1976. Proceedings: Coupling between cutaneous nerves.. https://pubmed.ncbi.nlm.nih.gov/175151/
Cite the original work for its findings. Save a collection to share your selection of sources.
KEEP EXPLORING
Anatomical characteristics of principal parasympathetic ganglia neurons on the guinea pig primary bronchus were analyzed, and the procedure for localizing the ganglia without the aid of staining for in vitro physiological studies is described. The neurons were tightly packed within a perineural sheath, and the cell bodies formed a homogeneous population based on size and shape. By using intracellular electrophysiological recordings, unstained neurons within these ganglia were characterized with suprathreshold depolarizing stimuli as having either accommodating action potential patterns (phasic neurons) or repetitive action potential patterns (tonic neurons). After determining whether a cell was tonic or phasic, it was injected with either horseradish peroxidase or Neurobiotin for characterization of its dendrites. There were no differences between tonic and phasic neurons, and both exhibited the following: (1) dendrites were multiple and branching; (2) all processes (axon and dendrites) arose from a circumscribed area on the somatic surface; (3) the initial direction of the processes was usually toward the center of the ganglion, creating a very dense intraganglionic neuropil; (4) tapering processes (presumed dendrites) extended beyond the border of the perineural sheath; and (5) many processes terminated with bouton-like swellings near the somatic surfaces of neighboring neurons within the same ganglion. Electron microscopic examination of dendritic and cell body membranes revealed that greater than 90% of the synapses occurred on dendrites. Based on immunohistochemical staining, all neurons were calbindin negative. These results indicate a relatively homogeneous population of neurons in bronchial parasympathetic ganglia displaying dendritic characteristics compatible with complex integrative properties.
Physical exercise increases brain activity through mechanisms not yet known. We now report that in rats, running induces uptake of blood insulin-like growth factor I (IGF-I) by specific groups of neurons throughout the brain. Neurons accumulating IGF-I show increased spontaneous firing and a protracted increase in sensitivity to afferent stimulation. Furthermore, systemic injection of IGF-I mimicked the effects of exercise in the brain. Thus, brain uptake of IGF-I after either intracarotid injection or after exercise elicited the same pattern of neuronal accumulation of IGF-I, an identical widespread increase in neuronal c-Fos, and a similar stimulation of hippocampal brain-derived neurotrophic factor. When uptake of IGF-I by brain cells was blocked, the exercise-induced increase on c-Fos expression was also blocked. We conclude that serum IGF-I mediates activational effects of exercise in the brain. Thus, stimulation of the uptake of blood-borne IGF-I by nerve cells may lead to novel neuroprotective strategies.
In the avian auditory brainstem, nucleus magnocellularis (NM) functions to relay phase-locked signals to nucleus laminaris for binaural coincidence detection. Although many studies have revealed that NM neurons exhibit intrinsic physiological and anatomical specializations for this purpose, the role of inhibition has not been fully explored. The present study characterizes the organization of GABAergic feedback to NM. Anterograde and retrograde labeling methods showed that NM receives a prominent projection from the ipsilateral superior olivary nucleus (SON). The functional features of this projection were explored in a brain slice preparation. Stimulating fibers from the SON evoked long-lasting, depolarizing responses in NM neurons that were blockable by bicuculline, a GABA(A) receptor antagonist. The slow time course of these responses allowed them to undergo temporal summation during repetitive stimulation. The summed GABAergic response was capable of blocking spikes generated in NM neurons by suprathreshold current injection. This inhibitory effect was attributable to a large reduction in input resistance caused by a combination of the opening of a GABAergic Cl(-) conductance and the recruitment of a low-voltage activated K(+) conductance. This large reduction of input resistance increased the amount of current necessary to drive NM neurons to threshold. The results lead us to propose that GABAergic inhibition enhances phase-locking fidelity of NM neurons, which is essential to binaural coincidence detection in nucleus laminaris.